Increased air tightness in new energy-efficient housing has led to serious problems with excessive indoor moisture in winter as well as with other trapped indoor air contaminants. Heat recovery ventilation systems are being used increasingly
Contains articles on rain penetration and moisture damage in residential construction, moisture sources in houses, control of surface and concealed condensation, and ventilation of houses. Illustrates the various types of condensation problems that may occur, explains the active processes involved in some of these problems and discusses in detail the principal factors surrounding these phenomena i.e. sources of moisture, choice of construction detail, and current ventilation practice.
The air infiltration component of house ventilation is calculated and discussed in relation to winter space heat losses and rneasures necessary to control moisture. The airtightness of 80 houses sampled from three major urban areas was inspected for association with location, external cladding materials, and design features such as the shape and complexity of the building envelope. A useful correlation of airtightness with envelope complexity emerged which gives a coarse but useful way of forecasting airtightness from building design information.
Several physical phenomena which may contribute to moisture migration from the crawl space to the living spaces in houses are outlined. Results of two projects to monitor moisture migration are presented.
The installation of much tighter windows has led to reduced rates of natural ventilation in German dwellings. This has resulted in increased indoor air humidity and condensation formation on the inner surfaces of external building elements with thermal bridges. Notes the areas most at risk from condensation and mould, in particular corners of outside walls and along the ceiling angle.
Recent work has demonstrated the existence of daily and seasonal cycles in attic moisture parameters. Over the course of a day, the attic air humidity may vary by a factor of three, and during the course of a winter there isstorage of perhaps
The theoretical background, admittance measurements and experimental work on interstitial condensation in lightweight roofs caused by air leakages is discussed. Describes a theoretical model of condensation behaviour taking into account moisture transfer by air flow as well as diffusion. Gives the air flow admittance for various roofing materials, ceiling systems and different roof-sections. Experimental results agreed well with the theoretical model.
This report addresses the factors causing water vapour problems and provides insights into the solutions available with particular emphasis on vapour barrier paints. Concludes that 1. moisture flow in structures is a dynamic, systemic process of multiple variables, and therefore requires an integrated approach for management, 2. retrofit applications offer an entirely different set of physical and economic considerations than are found in new construction and therefore require a different approach, 3.
Current moisture analysis methods for walls ignore air leakage effects or are not directly applicable to multilayered walls. Mathematical equations were developed for water vapour flow, vapour pressures, and moisture accumulation under steady state conditions with homogeneous one dimensional air flow through a multilayered wall.
With correct application of vapour barriers the ventilation of building structures is in general not necessary, unless such barriers prevent the escape of trapped moisture from moisture-sensitive - especially organic - materials. Indoor and outd
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